Gear members



Feb. 5', 1929. 1,7o1g222 U. BELATI GEAR MEMBERS Filed March 19, 1928 `teeth Patented Feb. 5, 1929. ,I

y UNITED STATES 1,101,222 PATENT OFFICE.

UMBERTO BELATI, 0F TURIN,A ITALY.

GEAR MEMBERS.

Application led #arch 19, 1928, Serial No. 262,931, and in Italy April 15, 1927.

base line of the member and evolvingwithin p said line, that is on the opposite side of said line with respect to the teeth. The profile so lobtained is enclosed within a profile shaped to an involute of a circle drawn on the same base line, and` it is noticeably differentiated from the latter one only in the half portion corresponding with the tooth point.

The present invention is hereinafter described in connection with toothed wheels, but it may be embodied in ahy kind of ltoothed members as racks and the like.

On the annexed drawing Figure 1 shows diagrammatically the intermeshin portions of two toothed wheels having teet shaped to an involute of a circle; f

Figure 2 is a similar diagram in respect of wheels provided with teeth having a shape in accordance with the present invention;

Figure 3 illustrates the method for tracing this profile; v

Figure 4 shows to a larger scale the toothed profile in accordance with the present invention when compared with a tooth or conventional profile.

In Figure the driver and 2 to be the follower, the beginning of: the engagement of the first palr ofv teeth 3 3 takes place along a line which projects on point 3 because the body of tooth 3 meets the edge of the point of tooth 3. v

Suchy a fact causes tooth 3 to meet tooth 3.

.with the character of a shock or, in best conditions, the oil film spread on the sides of teeth is removed in registenwith the contact portion owin to minimum extent of the same and to very igh unitary pressure operative there.

u- Likewise, in the last pair of intermeshin 4-4 at a given time the front edge o the point of tooth 4 is in contact with-the side of tooth 4 this fact also producing the removal of the lubricating film spread on the same.

In both cases the contact between two teeth vproduces vibrations which, as known, are theA cause of noise produced by gears during their p operation.

1 in which it is assumed 1 to be By inspecting Figure 2 which reproduces the same conditions of Figure 1 in respect of wheels in which teeth are profiled to an involute of an arc of an Archimedean s iral according to this invention, it is foun that on the first contact of teeth 3 and 3. the latter one has in contact witlithe side of the companion one a curve portion of its side adjacent to its same never happens along a line edge but it takes place over a curve surface adjacentto the tooth point. i

Under these conditions the sides of the two teeth come into Contact with and are recessing from each other without shock and without producing an exceedingly high local -pressure capable of removing the oil film and therefore the operationvof Va gear made in the above described manner is entirely smooth and noiseless, as experienced in tests carried out.

To obtain gear shaped to an involute of an arc of an Archimedean spiral, the methods and means of general use forproducing teeth shaped to an involute of a circle may be, used, with the exception that instead of using a circular rim as base member for the rolling element, a rim is used having an Archimedean spiral as its directing line, said spiral thusoriginating from the base circle of the wheel and evolving within it. y I I As shown in Figure 3, to obtain the desired profile, as base arc a line 5 is assumed which is an are of an Arch-imedean spiral obtained by way of approximation-by tracing an arc of a circle with its centre lying on av radius at 45 with respect to the radius passing through the selected origin of the tooth pro- ',from its origin -oand carrying on said tangent segments-b, b-, -o, o-,.-Z, having the same length as the respective to -b b-, -o c-, -`d if-f a line 6 is obtained which defines the profile ofthe side of a tooth.y

' The decrement -a of the arev of spiral ma `vary. in accordance with circumstances an it will be directly proportional to the oint, `and similarly the Contact of tooth 44 with tooth 4 before of its recess from the wheels .having a profile,

los

diameter of the pitch circle of the Wheel. ByV4 way of example in the event of a pinion having a pitch .diameter of mm. 100, satisfactory results have been obtained by giving a value of labout 0.80 mm. to said decrement;

In a rack said decrement is proportional to the tooth pitch.

Figure 4 shows the comparison between a tooth according to this invention shown in full line and a conventional tooth shown in dotted line, and traced as an involute .of a circle.

AThe tooth aifcording to this invention comprises a portion -w-- consisting ot' a connecting curve as conventional, whichextends from the tooth root circle I up to base circle II and then an arc ot' an involute of an Archimedean spiral which coincides under l practical standpoint with an involute ot' a circle up to the pitch circle III and then a depressed portion -zenclosed within the circle-involute line up to top circle IV.

The described profile may of course be used in connection With spur Wheels, bevel pinions and spiral teeth pinions, racks and so on, as well as in the manufacture of cutters for Fellows machines for the construction of toothed wheels.

What I claim as my invention and desire to secure by UnitedStates Letters Patent 15:.-

' 1. In a gear member, a tooth whose sidev is profiled to an involute of an arcof an Archimedean spiral, said arc having its origin on the base line ot said tooth and developing towards the root ot said tooth.

2. In a gear wheel, a tooth whose side is profiled to an involute of an arc of an Archimedean spiral, said, arc having its origin on the base circle ot said wheel and developing within said circle.l

3. In a gear member, a tooth whose side is profiled to an invollite of an arc oi an Archimedean `spiral having a decrement proportional with the tooth pitch. said arc having its origin on the bas-e line et said tooth and developing towards the. root of said tooth.

4. In a gear wheel, a toot-11 whose side is profiled to an involute of an arc of an Archimedean spiral having a decrement proportional with the diameter ot the pitch circle ot' said wheel, said arc having its originfon the base circle ot said Wheel and developing Within said base circle.

In testunony whereoi I alix my slgnature.

UMBERTO BELATI. 

